The digital printing technology is a noncontact printing technology developing rapidly in recent years, and is featured by directly processing, transmitting and printing image data. Noncontact printing is so called because a drop-on-demand inkjet printing nozzle is adopted in digital printing, a series of tiny channels are formed in the nozzle, ink is squeezed out of these tiny channels through mechanical effect produced by a piezoelectric crystal, directly jetted to a predefined position on the surface of a printing substrate for imaging, and the distance between the nozzle and the surface of the printing substrate is generally kept at about 1 millimeter. Compared with a traditional printing mode, the digital printing technology saves processes of plate-making and the like, is short in printing cycle and high in efficiency, and particularly, has a simple and efficient solution for printing tasks with high printing complexity such as variable data and color gradient images.
The digital printing technology supports printing of multiple color images based on four colors of CMYK (namely cyan, magenta, yellow and black), the color images are formed by dot matrixes of different gray levels of the four CMYK colors, and for a printing process, a different number of ink droplets with different sizes are mixed to form images. The quantity of the ink droplets depends on transmitted data, which is just the characteristic of the digital technology. For multi-color printing, hardware systems of all panes can not be installed on the same physical position, but have certain physical distances, so inevitably, there is an overprinting problem among a plurality of panes, and this problem is called as a synchronous problem among the panes.
So-called synchronization means to ensure that a plurality of panes of the same page are printed on the same position of a printing substrate, thus forming a page of complete image. For alignment of the position, two dimensions of an X direction and a Y direction need to be covered. This needs to effectively control the transmitting moment and the printing moment of data on all panes, so that the pane data printed at different moments can be printed on the same position of the printing substrate.
In the existing digital printing technology, in one-time production process, namely in the printing process of a job, the sizes of pages of the printed job are the same. Even mass production, namely, production of pages with the same size and in a huger number, basically involves a one-time production process. In this case, synchronization among a plurality of panes only needs one-time overprinting. In terms of the concept of overprinting, it needs to find a solution to ensure that a plurality of panes of the same page is printed together. In traditional printing, some models need adjustment of the length of a plate cylinder, and some models need manual adjustment of the physical position of each pane. In the existing digital printing technology, similarly, different models need different overprinting methods, namely the physical position of each pane is manually adjusted, or the physical position is fixed and registration of following panes and preceding panes is ensured through delay of time.
However, with the increase of customer demands, not only is large-order production needed, but also small-order customers need to be dealt with. Printed products of the small-order customers fall into many categories and are inconsistent in page size, and the quantity of each order is small, and printing in this case is commonly known as short-run live printing. However, according to the existing digital printing mode, only one job with same page size can be printed at a time, and for jobs with different page sizes, overprinting and machine adjustment need to be conducted again, so that the production efficiency is inevitably reduced, and the proportion of cost of media (namely, printing substrates) required for overprinting and machine adjustment in the total cost is inevitably increased.